1. Field of the Invention
This invention relates generally to tattoos. More particularly, this invention relates to a tattoo that normally is not visible to the naked eye, but which becomes visible upon exposure to a source of ultraviolet radiation, such as sunlight or an ultraviolet lamp.
2. Prior Art
The art of tattooing has been known for many years. Traditional tattoos are applied by using needles or needle-like instruments to inject colored ink or dyes into the skin of the person receiving the tattoo. Consequently, traditional tattoos are permanent in nature and may be removed only with difficulty, if they may be removed at all. However, in many instances persons act impulsively when they have a tattoo applied. Because of changed circumstances, or for other reasons these persons may later change their mind, and may wish to have the tattoo removed or altered.
Moreover, even if a person continues to be satisfied with the tattoo and proudly displays it, there may be occasions when a tattoo is not appropriate or the person may otherwise then wish to not display it. In such instances, the person has little choice except to cover the tattoo with clothing, which itself may be inappropriate, or attempt to have the tattoo otherwise obscured or removed from sight.
At least partially because of these difficulties, temporary tattoos, or even jewelry that superficially appears as a tattoo, have been developed so that a person can apply a tattoo to be temporarily worn and then removed by washing, etc. However, the appeal of these temporary tattoos is limited by the fact that they are generally available only in predetermined designs, and the tattoo typically comes off when it becomes wet. Moreover, it may bleed onto clothing.
Accordingly, there is need for a permanent or semi-permanent tattoo that does not wash off in water and which will not bleed onto clothing, but which is not visible unless desired.
The invention provides a tattoo that is permanent or semi-permanent, does not wash off or bleed on clothes, and remains invisible until the wearer desires it to be seen.
More particularly, the invention comprises a photochromatic tattoo in which photochromic compounds normally invisible to the naked eye, but which become visible upon exposure to sunlight or other sources of ultraviolet radiation (UV), are embedded in the skin to create a tattoo. The photochromic compounds are mixed in a non-pigmented or clear carrier that is substituted for the normal pigmented ink or dye that is used to apply a tattoo. The tattoo thus remains invisible to the naked eye until it is exposed to UV.
Examples of suitable photochromic compounds are described in U.S. Pat. Nos. 5,581,090 and 5,730,961, the disclosures of which are incorporated in full herein by reference. As noted in the ""090 and ""961 patents, photochromic substances are known in the art for their utilization in optics as storage media or as a means to detect UV, such as, e.g., the photochromic ultraviolet detector disclosed in the ""090 patent. Among the large family of photochromic compounds are the spiropyrans and spiroxazines groups of molecules. These molecules are known for their property of changing from clear to a variety of colors and shades. Normally appearing as colorless, these spiro-compounds undergo a photochemical transformation to intensely colored form when exposed to UV. The ""961 patent, in particular, discloses a material which remains clear until exposed to UV and which then exhibits color and thus becomes visible. The active chemical disclosed in the ""961 patent is identified as a photochromic substance such as spiropyrans or spiroxazines molecules. However, this patent relates to a nail polish applied to the surface of the nails of a wearer, and does not relate to a tattoo applied transdermally to the skin of the wearer.
A carrier for the photochromic compounds could comprise an invisible skin-marking ink such as that made by Sirchie Finger Print Laboratories of Youngsville, N.C., under the name xe2x80x9cInvisible Skin Marking Ink #743xe2x80x9d, and described more fully in U.S. Pat. No. 5,878,155. However, other suitable commercially available, transparent, non-toxic carriers could be used to embed the photochromic compounds in the skin.
U.S. Pat. No. 5,166,345 describes a photochromic compound which exhibits high color density, is stable against heat and solvent, and which has a great repeating durability in coloring-decoloring cycles. For improved performance, the photochromic compound used to produce a tattoo in accordance with the present invention can be formulated using the teachings of this patent, the disclosure of which is incorporated in full herein, whereby the stability, durability and color intensity, for example, of the compound are optimized.
Further, the composition used to make the photochromatic tattoo of the invention may be formulated so that it is operative only for a predetermined period of time, e.g., days, weeks or months, etc., after which the photochromic composition is no longer effective to produce a visible tattoo when exposed to UV. Alternatively, or in addition, the composition may be formulated so that once exposed to UV, the tattoo will remain visible only for a predetermined period of time, e.g., minutes, hours or days, etc.